The anchoring effect of Nb-based MXenes lithium-sulfur batteries: A first-principles study

摘要

The dissolution and diffusion of S-species in the electrolyte are one of the most important reasons affecting the development of lithium-sulfur batteries. MXenes, a two-dimensional material which has received a lot of attention recently, is investigated in lithium-sulfur (Li-S) batteries due to its excellent properties. Most of the current reports focus on Ti-based MXenes materials, while there are few studies on Nb-based MXenes materials. In this paper, the interactions between lithium polysulfide and Nb_2C-MXenes as well as O-functionalization (Nb_2CO_2 and Nb_3C_2O_2) and S-functionalization (Nb_2CS_2 and Nb_3C_2S_2) are investigated by using density functional theory calculations (DFT). According to the calculated results, both O-functionalized and S-functionalized have sufficiently large adsorption energy to inhibit the shuttle effect which occurs during the cycling of Li-S battery. As a comparison, O-functionalized MXenes have a more suitable adsorption energy for Li-S battery cathode materials, while S-functionalized MXenes have a lower ion diffusion potential barrier. In addition, all studied materials retain their original metallic properties after adsorption of lithium polysulfide, which contributes significantly to the electrochemical performance of Li-S batteries during charging and discharging. The results may be useful for investigating high-performance storage materials with Nb-based MXene materials.